I can no longer play the game. Since the last update I have been unable to log in. The app fades to black at 90% load and shunts me back to the iOS. I am using an iPhone 4s at is 8.1.1 with no other apps running. I can see the ads but the app will crash as soon as I tap the x to close the ad.

Even though it looks like it only needs a few hundred MegaBytes for extra cache, you might need a GB of free disk so DK can get the chunk sizes it wants. (This has not been specifically admitted, but it seems to act this way.) Not sure on the numbers but low disk space is a known problem. And low RAM is a big problem too. Apps stay in memory a long time. On Android I have a way to "Kill All Tasks" and a way to Free Memory. Sorry I can't suggest how to do that on IOS but a reboot would do it, unless you have apps that load at startup and immediately hog memory. Maybe you just installed (or updated) newsmagazines or media players that preload various things.